It is generally said that jokes don't age well but time has been astonishingly kind to a line Gore Vidal wrote 40 years ago. At the Virginia Theatre on Broadway on Wednesday afternoon, during a revival of Vidal's 1960 hit The Best Man, the words brought gasps and applause.

The play is set during the deadlocked presidential convention of an unspecified party. As a winner refuses to emerge, one contender exasperatedly warns: "The way we're going, we'll never nominate anyone." A nothing line when written has become an accidental show-stopper. Gore Vidal has often mocked his distant politician cousin Albert Jr, but the vice- president who is so desperate to give up the vice has allowed his relative the biggest laugh of his writing career.

The humourist's constitution mandates that events such as the current American election mess are cited as proof that truth is stranger than fiction. In New York this week, I have been testing this contention by immersing myself in presidential fiction.

Three White House stories were produced to coincide with the 2000 election. Apart from the comeback of Vidal's play, they were Rob Lurie's movie The Contender, with Joan Allen as a Democrat senator attempting to become vice-president against Republican hostility; and a political-legal thriller, Protect and Defend, by the bestselling Richard North Patterson. Watched or read against a background of events which you couldn't make up, these campaign tales now face an unusually severe test for political fiction. Have the novelists and playwrights been out-plotted by reality?

Vidal's The Best Man would seem as certain to date as Bill Clinton on a Saturday night. But, if the roar which now greets the line about the possibility of never nominating anyone is a result of luck, the writer deserves it for his general far-sightedness. Much other dialogue - including one about Americans feeling more comfortable when being led by someone stupid - now take on the kick of topicality. Scenes detailing a loveless marriage of political convenience produced an uneasy stirring in a theatre a few blocks from a bookshop where the new senator from New York, Hillary Rodham Clinton, was about to make an appearance. All political fiction fears being overtaken by events. The Best Man had the happier feel that events had taken it over.

A few hours later, at a 25-screen multiplex on several levels above 42nd Street, there was a sense of heightened expectation in the audience before a screening of the presidential thriller, The Contender. The present electoral no-win situation has had on political fiction an effect similar to recreational drugs. Each speech seems more significant, every irony bigger.

The Contender (released in Britain next year) is, like Al Gore, caught between two administrations. Joan Allen's would-be vice-president is almost destroyed by Gary Oldman's McCarthyite Republican, waving faded stains on her sheets. The message - that sex should not be relevant to a politician's career - is a parting gift to Bill Clinton from the producer, his friend Steven Spielberg. But the image of politics as a dirty fight between parties more interested in victory than principles is helped by the Florida context and a reference to a vice-president's sudden death in office produced Cheney-inspired titters.

The film, though, is essentially a Clintonian fiction. Better adapted to the new unled America is Protect and Defend. With triple luck, Richard North Patterson's book has a title from the constitution, an illustration of the supreme court pillars on its cover and is published on December 12 - now the final legal deadline for the Florida arithmetic to cease. Inclining to the view that the White House is increasingly a frat-room for the nation's lawyers, the book follows a president attempting to appoint the next chief justice, but feels perfectly timed for a period in which the chief justice may appoint the next president.

There was a startling example in Britain a decade ago of a real politician helping the career of a fictional one: Andrew Davies's BBC adaptation of the Michael Dobbs novel House Of Cards, with Ian Richardson as a Tory schemer plotting the succession to a resigning prime minister, had the enormous good fortune to be broadcast in the week of Margaret Thatcher's fall.

Any American fiction writer who came up with such a neat plot coincidence on this occasion would have to be interrogated at once for close connections with God or the governor of Florida. But, competing with occurrences which could not have been foreseen, America's political fiction writers have proved surprisingly prescient. Broadway producers may have been knowingly cheeky in staging a play this autumn by a member of the Gore clan and casting an actor (Chris Noth from Sex and the City) who shares the current vice-president's bulky solemnity. But how odd that Vidal's play should depict deadlocked contenders.

And The Contender's portrayal of main parties' hatred of each other as the driving motivation of American politics draws on the Clinton impeachment, as did North Patterson's contention that American politicians are merely surrogates for the lawyers who truly run the country. But the 2000 election - being decided posthumously by animosity and attorneys - has shown in these writers an ability to predict the future issues which would make any focus group envious. None of these political narratives needed to be differently recounted.